Can I sell a game I write in Inform?

I’ve done a little searching here on the subject of the license and I think it’s allowed. Can anybody confirm or refute that?

The viability of such a project is another matter, of course…

Yes you definitely can and it has been done.

Good to know, thanks. I assume I must avoid using any extensions created by others, yes?

All extensions listed on the Inform extensions page are licensed under the Creative Commons Attribution license. So you’re perfectly free to use them in commercial products.

If you got an extension from somewhere else, you’d need to find out what its license is.

As long as you retain the banner, and keep the version command intact, you’re good to go!